An overspeed safety device that mechanically detects excessive car speed and triggers the safety gear to stop the car.
Full Definition
The elevator governor is a centrifugal speed-sensing device mounted in the machine room or at the top of the hoistway. It consists of a sheave driven by the governor rope connected to the car, carrying rotating flyweights. When car speed exceeds the trigger speed (set to 115% of rated speed per EN 81-20), centrifugal force causes the flyweights to pivot outward and engage a jaw or trip lever, gripping the governor rope. This tension is transmitted mechanically to the safety gear levers on the car sling, causing the safety gear to clamp the guide rails and arrest the car. A second, higher trigger speed initiates the overspeed switch that also cuts power. Governors are type-tested and must be trip-tested during periodic inspection. Re-setting requires qualified personnel.
